EXAMS, schools, colleges and universities all shut down yesterday - with parents of young children angry at being given little notice.
School authorities faced criticism at the lateness of the announcement, which came after 10pm on Sunday on social media.
A similar announcement in the Republic was made shortly after 3pm on Sunday.
The message from the Department of Education only advised that schools "should" close.
Parents and schools said this caused confusion, with some schools even initially announcing they planned to stay open.
The closure of the north's further education colleges was confirmed even later - in a press release issued after 1am.
Ulster University closed its four campuses yesterday while Queen's University Belfast also cancelled classes.
Child Protection Training due to take place in the North West Teachers' Centre was postponed as were Essential Skills exams.
More than 1,000 schools from nursery to post-primary were advised to keep closed. The Department of Education also said youth service provision should close.
Some parents were angry that the lateness of the announcement by the department gave them little time to arrange childcare.
It was not until after 10.20pm that Stormont issued a tweet, saying the department "has announced that all schools should close as precautionary measure in light of weather warnings".
However, the original tweet, which was sent by the NI Executive account, would only have been seen by people following both it and the Department of Education's account.
Some said they learned of the decision when a message appeared on television screens during Match of the Day.
An official press release was issued at 10.45pm.
Many schools said they received no official notification, among them Tildarg PS in Ballyclare.
Fey Cole, a lecturer at South West College, was among those angered.
"Announced at 10.22pm when most teachers will be in bed preparing for day ahead. Ridiculous for both parents and teachers announcing this time," she posted on Twitter.
The use of the world "should" was criticised by many, among them @Irishslang on Twitter who said: " This is a disgraceful message leaving parents wondering at 11pm the night before."
Andrew McCreery said: "Can we have clarification on "should close" if its a recommendation only why is it posted on a public forum leaving uncertainty?"
Joanne Dunne added: "Why has there been no official email to principals? Hearing about this over social media is not acceptable."
Asked about the late announcement, the department said it took the decision following a meeting of the Multi-Agency Responders Group.
It took place late on Sunday evening in relation to contingency plans for public services in Northern Ireland.
"Weather alerts were continually monitored throughout the weekend in addition to decisions being taken across other agencies," a spokeswoman said.
"Given the severity and timing of the weather warnings for Northern Ireland, with the highest risk being when pupils will be travelling home from school, officials in the department made the decision to close schools to ensure the safety of all children. We understand the difficulties this causes to parents and schools, however the department's priority is to the children and young people that it has responsibility for."
SDLP assembly member Colin McGrath said his party had pressed for an earlier decision after a similar announcement in the Republic.
He said the decision in the north was welcome but "very late".
"Parents will struggle to arrange childcare and many children will already have their lunches packed for school in the morning," he said.
"This really is very late in the day."
The CCEA postponed Essential Skills Application of Number, Level 1 and Level 2 exams due to be taken by 260 candidates across 20 test centres.
All centres were personally contacted and advised of the change of date to Thursday of next week.
"All other Essential Skills examinations scheduled for Tuesday 17 and Wednesday 18 October will take place as scheduled. Candidates unable to take the rescheduled examinations on Thursday 19 October will have another opportunity to take the examinations in January 2018," a spokesman said.
